Sleeve for logging while drilling electromagnetic sensor

ABSTRACT

An apparatus for measuring a characteristic of an earth formation includes a drill collar configured to be inserted into a borehole of the earth formation, an electromagnetic sensor on the drill collar, and a non-conductive sleeve surrounding a circumference of the drill collar including the electromagnetic sensor and configured to press directly against the electromagnetic sensor.

BACKGROUND

Boreholes are drilled deep into the earth for many applications such ascarbon sequestration, geothermal production, and hydrocarbon explorationand production. Electromagnetic sensors may be used to collectinformation about the earth around the borehole during a drillingoperation. However, metal shields positioned around the electromagneticsensors to prevent damage to the sensors may interfere withelectromagnetic signals transmitted by the sensor and received by thesensor.

BRIEF SUMMARY

Disclosed is an apparatus for measuring a characteristic of an earthformation. The apparatus includes a drill collar configured to beinserted into a borehole of the earth formation, an electromagneticsensor on the drill collar, and a non-conductive sleeve surrounding acircumference of the drill collar including the electromagnetic sensorand configured to press directly against the electromagnetic sensor.

Also disclosed is a system for an apparatus including a drill collar, asensor located around the drill collar, and a non-conductive sleevecovering an entire outer surface of the sensor and configured to contactthe outer surface of the sensor.

Further disclosed is a method including providing a drill collar in awellbore, the drill collar including a sensor located on the drillcollar and a non-conductive sleeve entirely covering the sensor andsubjecting the non-conductive sleeve to a pressure to press thenon-conductive sleeve against the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 illustrates a drill pipe segment according to an embodiment ofthe present disclosure;

FIGS. 2A and 2B illustrate a portion of the drill pipe segment accordingto an embodiment of the present disclosure;

FIG. 3 illustrates a portion of a drill pipe according to anotherembodiment of the present disclosure; and

FIG. 4 illustrates a method according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method presented herein by way of exemplification and notlimitation with reference to the Figures.

FIG. 1 illustrates a portion of a drill pipe 100 according to oneembodiment of the present disclosure. The portion of the drill pipe 100includes a drill collar 110, a sensor 120, and a sleeve 130 covering thesensor 120 in a radial direction.

The drill collar 110 may be made of a metal material such as steel andin one embodiment, the drill collar 110 includes a conduit 111 totransmit wires, cables, fluids, or any other materials. For example,wires or cables may extend through the conduits 111 of multiple drillcollars 110 connected end-to-end. Likewise, fluids maybe transmittedthrough the conduits 111 of multiple drill collars 110 connectedend-to-end. In one embodiment, the drill collar 110 includes multipleconduits 111.

The sensor 120 is located on the drill collar 110 radially outward froma center axis of the drill collar. In one embodiment, the sensorsurrounds the drill collar 110. For example, the sensor may be anelectromagnetic sensor and may include one or more coils wound around anoutside surface of a sensor and recessed in the drill collar 110. In oneembodiment, the sensor 120 includes a coil portion 121 and a baseportion 122. The base portion 122 may include one or more materials,such as magnetic materials, non-magnetic materials, ferromagneticmaterials, insulating materials, conductive materials, non-conductivematerials, or other materials according to design considerations of thesensor 120. For example, in one embodiment the base portion 122 is ashielding chassis that isolates the coil portion 121 from the drillcollar 110, which may be made of metal. In one embodiment, the sensor120 is recessed in the drill collar 110, such that an outer surface ofthe drill collar 110 has a diameter greater than an outer diameter ofthe sensor 120.

The sleeve 130 extends over an entire outer surface of the sensor 120.In one embodiment, the sleeve 130 has a cylindrical shape. In oneembodiment, the sleeve 130 is formed to have no holes or stress risers,such as welds, ridges, or other protrusions. For example, the sleeve 130may be formed in an extrusion process to maintain uniform materialproperties and smooth surface.

In one embodiment, the sleeve 130 is non-conductive, and in oneembodiment the sleeve 130 is a non-metal material. For example, in oneembodiment, the sleeve 130 is made of a high-temperature rated plasticor polymer, such as polyether ether ketone (PEEK).

The sleeve 130 is located over the sensor 120 to have either a smallspace or no space 132 between the sleeve 130 and the sensor 120 when noinward pressure is applied to the sleeve 130, or when a sea-level orabove-ground-level pressure is applied to the sleeve 130. However, thesleeve 130 may be configured to press against the sensor 120 whenpressure is applied to the sleeve 130. In embodiments of the presentdisclosure, the pressure is a pressure within a well bore of an earthformation. For example, in one embodiment a predetermined pressure levelis determined at which a drill collar 110 will operate in a well bore,and the sleeve 130 is configured of such a thickness and material topress against the sensor 120 at the predetermined pressure.

When the drill pipe 100 is inserted into a well-bore, pressures in thewell-bore may press against the sleeve 130, which then may press againstthe sensor 120. The pressures in the well bore may be generated due tohydrostatic pressures within the well bore including pressures resultingfrom a depth of the well bore, fluid in the well bore, and pressuresgenerated due to a drilling operation performed by a drill connected tothe drill pipe 100.

In embodiments of the present disclosure, the sleeve 130 is configuredto press against substantially an entire outer radial surface of thesensor 120. In the present specification and claims, the term“substantially the entire surface” refers to at least 80% of the outerradial surface of the sensor 120, such as 90% or 95% of the outer radialsurface of the sensor. In embodiments of the present disclosure, the gap132 between the sleeve 130 and the sensor 120 is very small, such asbetween 1/1000 inch and 1/10,000 inch, such that the sleeve 130 deformsonly a very small amount when pressure is applied to the sleeve 130. Inother words, the gap 132 may be sufficient only to allow for statisticalvariations in parts dimensions, such as sensor 120 dimensions or drillcollar 110 dimensions.

In embodiments of the present disclosure, the drill collar 110 includesa slot or groove 112 located at axial ends of the sleeve 130 to receivea sealing member, such as an O-ring, to form a hermetic seal between thesleeve 130 and the drill collar 110 to prevent fluids from contactingthe sensor 120. When a pressure is applied to the sleeve 130, the sleeve130 applies pressure to the sealing members, strengthening the hermeticseal.

FIGS. 2A and 2B further illustrate a portion of the drill pipe 100according to embodiments of the present disclosure. For purposes ofdescription, FIGS. 2A and 2B illustrate only sections of the drill pipe100 corresponding to the portion A indicated in FIG. 1.

The drill pipe 100 includes the drill collar 110 having a recess formedtherein to receive the sensor 120, the seal members 140, and the sleeve130. The sensor 120 includes the base portion 122 and the coil portion121, and an inner radial surface 121 b of the coil portion 121 contactsan outer radial surface 122 a of the base portion 122. The drill collar110 includes the grooves 112 to receive therein the seal members 140. Inone embodiment, the seal members 140 are O-rings that encircle the drillcollar 110.

The sleeve 130 may be located on the seal members 140, and the sleeve130, seal members 140, and drill collar 110 may together form thehermetic seal to prevent air and fluid from contacting the sensor 120.When no pressure is applied to the non-conductive sleeve 130, asillustrated in FIG. 2A, a gap 132 may be present between an inner radialsurface 130 b of the sleeve 130 and an outer radial surface 121 a of thecoil portion 121 of the sensor 120. In one embodiment, the gap 132corresponds to an extent that the seal members 140 extend radiallyoutward form the sensor 120 and the recessed portion of the drill collar110.

In one embodiment, the gap 132 is of a sufficient size only to allow forstatistical variations in parts dimensions, such as sensor 120dimensions or drill collar 110 dimensions. In other words, the gap 132may be designed to be as close to zero as allowable within predetermineddesign tolerances of the part dimensions. Example widths of the gapinclude 1/1,000 inch and 1/10,000 inch. In one embodiment, an outerradial surface 130 a of the sleeve 130 is flush with an outer surface ofthe drill collar 110 when no pressure P is applied to the sleeve 130.

When a pressure P is applied to an outer radial surface 130 a of thesleeve 130, the sleeve 130 presses against the seal members 140 and thesensor 120. In particular, the inner radial surface 130 b of the sleeve130 presses against an outside radial surface 121 a of the coil portion121. In one embodiment, when the pressure P is applied to the sleeve130, the axial ends of the sleeve 130 are maintained substantially flushwith the outer surface of the drill collar 110, and an axial centerportion inward from the ends is compresses radially inward to contactthe seal members 140 and the sensor 120. Since the gap 132 is verysmall, in the range of 1/1000 inch to 1/10,000 inch, the compression ofthe sleeve 130 is also very small and does not cause stress risers toform on the outer surface 130 a of the sleeve 130.

Since the hydrostatic pressure P is transferred to the seal members 140and the sensor 120, the sleeve 130 is maintained in position, evenduring a drilling operation. In addition, the sleeve 130 is supported bythe drill collar 110 via the sensor 120, while isolating the sensor 120from fluids. The sensor 120 is thereby protected from damage from fluidin the drill bore and slippage of the sleeve 130. In addition, thecompressive load of the hydrostatic pressure P further protects thesleeve 130 from tensile failure. In addition, the high level of pressureP against the sleeve 130 mitigates the effects of high coefficients ofthermal expansion of non-conductive or non-metallic sleeves.

In one embodiment of the present disclosure, the sleeve 130 is anon-metallic sleeve, such as a high-temperature rated plastic or polymersleeve. In one embodiment, a thickness of the sleeve 130 in a radialdirection is at least 5% a diameter of the sleeve 130. For example, thethickness of the sleeve 130 may be between 5% and 20% of the diameter ofthe sleeve 130.

In one embodiment, the sleeve 130 presses directly against the sensor120 when the pressure P is applied to the outer radial surface 130 a ofthe sleeve 130. In another embodiment, a non-conductive or non-metalliclayer is formed on the sensor 120, such as around the coil portion 121of the sensor 120, and the sleeve 130 presses against the non-conductiveor non-metallic layer.

FIG. 3 illustrates a segment of drill pipe 300 according to oneembodiment of the present disclosure. The segment of the drill pipe 300includes a drill collar 310 and sleeve 330. As illustrated previously inFIGS. 1, 2A, and 2B, the sleeve 330 covers a sensor and an insideportion of the drill collar 310. In other words, the drill pipe 300,drill collar 310 and sleeve 330 may correspond to the drill pipe 100,drill collar 110, and sleeve 130 of FIGS. 1, 2A, and 2B.

The drill pipe 300 includes a raised portion 340 at each end of thesleeve 330. In one embodiment, the raised portion 340 includes aplurality of separated studs, platforms, plates, or pads 350 that extendradially outward from the drill collar 310 and are arranged around anouter circumference of the drill collar 310. In another embodiment, theraised portion is a single ring that extends around the circumference ofthe drill collar 310.

The raised portion 340 may be made of a material harder than the drillcollar 310. For example, in one embodiment, the drill collar 310 is madeof steel and the raised portion 340 is made of carbide. The raisedportion 340 has a diameter D2 larger than a diameter D1 of the drillcollar 310 and the sleeve 330. For example, in an embodiment in whichthe raised portion 340 is made of carbide pads 350, the outer surfacesof the carbide pads 350 correspond to a diameter D2 of the raisedportion 340, and the diameter D2 of the raised portion 340 is greaterthan a diameter D1 of the sleeve 330. Accordingly, when the drill pipe300 is located in the well bore, the raised portion 340 provides astandoff of the sleeve 330 from the drill bore wall. In one embodiment,a diameter D2 of the raised portion 340 is between approximately 1% and10% greater than the diameter D1 of the sleeve 330.

An end of the sleeve 330 is separated from the raised portion 350 by adistance L1. The distance L1 is configured to ensure that the raisedportion 340 provides a standoff for the sleeve 330 from a well borewall. For example, when the raised portion 340 is larger, the distanceL1 may be larger, or the sleeve 330 may be located farther from theraised portion 340. Conversely, when the raised portion 340 is smaller,the end of the sleeve 330 is located closer to the raised portion 340.In one embodiment, the distance L1 is less than a diameter D1 of thenon-conductive sleeve.

FIG. 4 illustrates a method according to one embodiment of thedisclosure. In block 401, a drill pipe including a drill collar, asensor located around the drill collar, and a non-conductive ornon-metallic sleeve located around the sensor and drill collar isprovided into a well bore of an earth formation. The drill pipe may bethe drill pipe 100 or 300 of FIGS. 1 and 3, respectively. The well boremay include fluid therein, such as drilling mud, water, petroleum, andother liquid. In block 402, a drilling operation is performed. Each ofthe providing the drill pipe into the well bore and performing thedrilling operation may result in an increase in pressure on the sleeveof the drill pipe. As the pressure increases on the sleeve, the sleevepresses against the sensor and is supported by the drill collar. Sincethe sleeve is pressed against the sensor and the drill collar, thesensor is protected from damage from fluid in the drill bore andslippage of the non-conductive sleeve. In addition, the non-conductivesleeve is protected from tensile failure and the effects of highcoefficients of thermal expansion.

In operation 403, a sensing operation is performed by the sensor duringthe drilling operation. Since the non-conductive sleeve is pressedagainst the sensor, the sensor is protected from damage and fluidexposure during the drilling operation. In embodiments in which thesleeve is a non-conductive or non-metallic sleeve, the sensing operationis improved relative to metallic or conductive sleeves that adverselyaffect sensing signals, such as electromagnetic signals.

According to embodiments of the present disclosure, a non-conductive ornon-metallic sleeve is used to protect a sensor, preventing signal lossby the sensor. The sleeve is configured to press against the sensorduring operation, such as under pressure in a well bore, to preventslippage and form a hermetic seal over the sensor. Raised portions mayalso be provided at ends of the sleeve to further protect the sleevefrom damage in the borehole.

Elements of the embodiments have been introduced with either thearticles “a” or “an.” The articles are intended to mean that there areone or more of the elements. The terms “including” and “having” areintended to be inclusive such that there may be additional elementsother than the elements listed. The conjunction “or” when used with alist of at least two terms is intended to mean any term or combinationof terms. The terms “first” and “second” are used to distinguishelements and are not used to denote a particular order. The term“couple” relates to coupling a first component to a second componenteither directly or indirectly through an intermediate component.

It will be recognized that the various components or technologies mayprovide certain necessary or beneficial functionality or features.Accordingly, these functions and features as may be needed in support ofthe appended claims and variations thereof, are recognized as beinginherently included as a part of the teachings herein and a part of theinvention disclosed.

While the invention has been described with reference to exemplaryembodiments, it will be understood that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the invention. In addition, many modifications will beappreciated to adapt a particular instrument, situation or material tothe teachings of the invention without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. An apparatus for measuring a characteristic of anearth formation, comprising: a drill collar configured to be insertedinto a borehole of the earth formation; an electromagnetic sensor on thedrill collar; and a non-conductive sleeve surrounding a circumference ofthe drill collar including the electromagnetic sensor and configured topress directly against the electromagnetic sensor.
 2. The apparatus ofclaim 1, further comprising: sealing members at axial ends of thenon-conductive sleeve to form an airtight seal with respect to the drillcollar and the non-conductive sleeve.
 3. The apparatus of claim 2,wherein the sealing members are located radially between thenon-conductive sleeve and the drill collar.
 4. The apparatus of claim 1,wherein the non-conductive sleeve is a non-magnetic sleeve.
 5. Theapparatus of claim 1, wherein the non-conductive sleeve is made of apolymer.
 6. The apparatus of claim 1, wherein the drill collar includesraised portions at axial ends of the non-conductive sleeve, the raisedportions having diameters greater than a diameter of the non-conductivesleeve.
 7. The apparatus of claim 6, wherein the raised portions aremade of a material having a hardness greater than a hardness of thedrill collar.
 8. The apparatus of claim 6, wherein a distance from theends of the non-conductive sleeve to the raised portions is less than adiameter of the non-conductive sleeve.
 9. The apparatus of claim 1,wherein the non-conductive sleeve is configured to press againstsubstantially an entire outer radial surface of the electromagneticsensor.
 10. The apparatus of claim 1, wherein the electromagnetic sensoris configured to press against the drill collar based on thenon-conductive sleeve pressing against an outer radial surface of theelectromagnetic sensor.
 11. An apparatus, comprising: a drill collar; asensor located around the drill collar; and a non-conductive sleevecovering an entire outer surface of the sensor and configured to contactthe outer surface of the sensor.
 12. The apparatus of claim 11, whereinthe non-conductive sleeve forms an airtight seal with the drill collar.13. The apparatus of claim 12, further comprising sealing memberslocated at axial ends of the non-conductive sleeve to press against thenon-conductive sleeve to from the airtight seal with the drill collar.14. The apparatus of claim 11, wherein the non-conductive sleeve isconfigured to compress inwardly in a radial direction toward the sensorwhen a predetermined pressure is applied to the non-conductive sleeve.15. The apparatus of claim 14, wherein the predetermined pressure is oneof a predetermined ranges of pressures corresponding to a pressurewithin a wellbore during a drilling operation.
 16. The apparatus ofclaim 11, wherein the non-conductive sleeve is made of ahigh-temperature rated plastic.
 17. The apparatus of claim 11, whereinthe sensor is an electromagnetic sensor having a coil wound around thedrill collar.
 18. The apparatus of claim 11, wherein a thickness of thenon-conductive sleeve is at least 5% of the diameter of thenon-conductive sleeve.
 19. The apparatus of claim 11, wherein thenon-conductive sleeve has a smooth outer surface free of stress risers.20. A method, comprising: providing a drill collar in a wellbore, thedrill collar including a sensor located on the drill collar and anon-conductive sleeve entirely covering the sensor; and subjecting thenon-conductive sleeve to a pressure to press the non-conductive sleeveagainst the sensor.
 21. The method of claim 20, wherein subjecting thenon-conductive sleeve to the pressure includes performing a drillingoperation in the wellbore.
 22. The method of claim 21, furthercomprising operating the sensor to obtain information about an earthformation while performing the drilling operation in the wellbore.